climate
Black walnut grows best in full sun.
soil
Black walnut requires well-drained soil that has a neutral pH. Poorly
draining soil may lead to root rot, which is a condition that deteriorates
the structure and function of the plants root system. Black walnut trees thrive in
rich loamy or sandy soil.
growing
The best way to propagate this plant is by sowing seeds. Collect the nuts
and plant in moist, well-drained, rich soil during the fall or spring after
a cold stratification of 90-120 days. It is recommended to remove the husk.
Seedlings emerge in April or May the first or second spring after the seed
is planted. Although young trees will sometimes begin producing nuts when
only 4-6 years old, it usually takes 20 years before a tree will produce a
large crop of nuts.
harvesting
As black walnuts ripen, the husk changes from solid green to yellowish
green. Walnut juice leaves a dark stain, so wear gloves when you handle
unhusked walnuts. Press on the skin of the walnut with your thumb; ripe nuts
will show an indentation. Weekly monitoring is important as nuts will mature
over a four to six week period. Try to harvest the ripe nuts directly from
the tree, ahead of the squirrels. If the nuts are too difficult to reach,
they can be collected after they fall from the tree during frosts. Often the
husk of mature nuts has dried and cracked. Husks must be removed before you
store black walnuts.
preserving
Hulling walnuts, removing the husk, must be done prior to storage and can be
a difficult and messy task. The indelible dye from the husk stains hands,
clothes, tools and work surfaces. If you are working with dry nuts, the husk
can be removed by applying pressure to the ends of the nut. This can be done
by pounding side to side with a hammer, of course while wearing safety
glasses.
The husks can also be softened in a container filled with a slurry of three
parts nuts to one part water and a handful of gravel. Stir the mixture
vigorously. It may take more than one attempt to completely remove the husks. If
you are hulling a large quantity of nuts, the slurry can be used in a small
portable cement mixer.
After hulling, wash the unshelled nuts. After husks have been removed, the nuts
must be cured. Curing prepares the walnuts for storage and allows the walnut
flavor to develop. To cure black walnuts, stack the clean hulled nuts in shallow
layers only two or three nuts deep. Place the nuts in a cool, dry,
well-ventilated area out of direct sunlight for two weeks.
To be certain nuts have cured adequately, break open a sample nut. When the nut
is dry enough to store, its kernel will break crisply, with a sharp snap. If
cured improperly, nuts will mold.
After curing, store unshelled nuts in a well-ventilated area at 60°F or less.
Cloth bags or wire baskets allow adequate air circulation and discourage
development of mold. Try to keep the relative humidity fairly high, ideally
about 70%. Nut shells will crack and the kernels spoil if nuts are stored in too
dry an area.
When you're ready to shell the nuts, moisten them to keep the kernels from
shattering. Soak the walnuts in hot tap water for about 24 hours. Drain and
replace the hot water and soak the nuts for two more hours. Cover the nuts with
moist cloths until you're ready to crack the shells.
After shelling, nut meats can be stored in several ways: at room temperature,
refrigerated or frozen. If you plan to store the nutmeats in a container at room
temperature and use them within a few weeks, first bake them at 215° for 10 to
15 minutes. Nutmeats can be refrigerated in a jar or plastic bag for up to nine
months without baking. Nutmeats can also be frozen for longer term storage, but
use them within two years.